WATERBURY — The chairman of Waterbury’s Conservation Committee on Monday brought concerns to the Select Board about invasive plant species being mingled in sand and gravel piles that the town uses for road repairs.

Allan Thompson, the Conservation Committee chairman, said Tuesday the entire back of a sand pile near the post office in Waterbury Center is covered with phragmites, a large perennial grass found in wetlands. Thompson also said that Japanese knotweed, another large perennial, is partly visible from a village stockpile on Moran Lane.